How to modify bits in an integer?

Question

I have an integer with a value 7 (0b00000111) And I would like to replace it with a function to 13 (0b00001101). What is

Answer 1

You just need:

def set_bit(v, index, x):
  """Set the index:th bit of v to 1 if x is truthy, else to 0, and return the new value."""
  mask = 1 << index   # Compute mask, an integer with just bit 'index' set.
  v &= ~mask          # Clear the bit indicated by the mask (if x is False)
  if x:
    v |= mask         # If x was True, set the bit indicated by the mask.
  return v            # Return the result, we're done.

>>> set_bit(7, 3, 1)
15
>>> set_bit(set_bit(7, 1, 0), 3, 1)
13

Note that bit numbers (index) are from 0, with 0 being the least significant bit.

Also note that the new value is returned, there's no way to modify an integer "in place" like you show (at least I don't think so).